Other related questions:

Question:
According to ITU-T suggestions, the standard LP_UNEQ alarm is inserted if no lower-order service is configured. However, some OSN devices cannot detect the LP_UNEQ alarm for triggering SNCP switching. Why?
Analysis:
Board hardware restrictions. Some boards can be upgraded to resolve the problem, whereas some cannot.
Answer:
No version of SSN1GXCSA, SSN1EXCSA, or SSQ1CXL supports LP_UNEQ detection.

ODUk SNCP is classified into SNC/I, SNC/N, and SNC/S. The difference between the three protection schemes lies in that they have different monitoring capabilities and therefore have different trigger conditions.

The switching detection time (unit: 10 ms) described in the product documentation is used in cascading scenarios.
The SD enable status for protection determines whether protection switching is triggered when an SD condition is detected.
Fast SD protection switching is based on bit errors and implemented by setting the DEG detection time window (ms) of the SM overhead.

The conditions for triggering automatic ODUk SNCP switching are as follows:
The board cannot be detected (for example, the board is removed or undergoes a cold reset).
There are board alarms indicating SF and SD.